Reliability, agreement, and responsiveness of a 6-minute walk/run test in patients with heart disease

Background: The 6-minute walk test (6MWT) is widely used to assess exercise tolerance in cardiac rehabilitation (CR). However, previous research shows it to be insufficiently responsive, especially for patients with a relatively high maximal exercise tolerance at baseline. We therefore designed a 6-minute walk/run test (6MWRT), which has the same duration as the 6MWT but allows running. The objective of this study was to determine the test-retest reproducibility and responsiveness of this 6MWRT. Design: Responsiveness was investigated in a prospective cohort study among a group of patients entering CR at Maastricht University Medical Center, with a cross-sectional part to assess the test-retest reproducibility. Methods: Test-retest reproducibility (reliability and agreement) was investigated using the intraclass correlation (ICC) and a Bland-Altman plot of two measurements implemented in the first week of rehabilitation. Responsiveness of the 6MWT and the 6MWRT was calculated using the standard response mean (SRM) over a 6-week period. Results: The first reproducibility analysis included 34 patients, the second 22 patients. The ICCs were 0.935 and 0.906, respectively, with limits of agreement of +/- 79 and +/- 61 m. The responsiveness analysis included 27 patients. The SRM values were 0.83 for the 6MWT and 0.71 for the 6MWRT. Conclusions: Although the 6MWRT is a reproducible test in CR, its responsiveness is not superior to that of the 6MWT. We therefore prefer the conventional 6MWT as an evaluative measurement in CR and advise against using the 6MWRT as (evaluative) measurement in CR for this purpose.